Angle adjustable vane suspension

ABSTRACT

A vane suspension for angle adjustable mounting of a vane (6) in a hub (1), comprising a seat (3) in the hub and a mounting part on the vane (6). The mounting part on the vane comprises a stud (16) and a shoulder (17) provided at the end of the stud with a partly spherical contact surface (19) facing the blade (15) of the vane, and in that the seat (3) of the hub has a hub shoulder (10) with a partly cylindrical contact surface (12) radially facing the center of the hub (2), which two surfaces are arranged to cooperate mutually by linear contact, whereby the position of the line (21, 21&#39;) is constant irrespective of the angular position of the vane in relation to the hub.

FIELD OF INVENTION

The present invention relates to an angle adjustable suspension of vanesin a hub, comprising a seat in the hub and a mounting part on the vane.

PRIOR ART

There is a need for adjusting the angles of vanes on blade wheels inorder to adjust the characteristics of the blade wheel to existingconditions and desires. There are solutions which allow adjustment ofthe angle of the vanes also during operation as well as automaticadjustment of the angle of the vane depending on current load.

U.S. Pat. No. 2,844,207 discloses an adjustable fan blade means, whereinthe fan blades can be adjusted individually when the fan wheel rests.The fan blades are axially locked, for uptake of rotational load, by alock washer which abuts a shoulder in the hub and the adjusted angularposition is maintained with the aid of a locking screw which is forcedagainst the blade stud, which extends through a peripheral hole in thehub. With this construction the torsional moment as well as the bendingmoment will be taken up only by the friction between the abutmentsurface of the locking screw and the periphery of the blade stud. Thissolution is not satisfactory for fastening of vanes being exposed tolarge loads and does not give sufficient safety margins for the uptakeof the rotational load and the bending moment.

DESCRIPTION OF THE INVENTION

The main object of the present invention is to provide an adjustablevane suspension in a hub, which gives a safe hold of the vane in the huband at the same time allows for a quick and exact individual angularadjustment of the vane.

This and other objects of the present invention are achieved by the vanesuspension according to the present invention which is characterized inthat the mounting part on the vane comprises a stud and a shoulderprovided at the end of the stud with a partly spherical contact surfacefacing the blade of the vane, and in that the seat of the hub has a hubshoulder with a partly cylindrical contact surface radially facing thecentre of the hub, which two surfaces are arranged to mutually cooperateby linear abutment, whereby the position of the line (21,21') isconstant irrespective of the angular position of the vane in relation tothe hub.

Through the cooperating, partly spherical and partly cylindrical contactsurfaces, respectively, an effective and secure uptake of the load fromthe rotational load through shearing is achieved. The design of therespective contact surfaces of the hub shoulder and the vane studresults in a compression load distributed in linear contact, thegeometrical position of which is constant at different angularadjustments of the vane. In practice, a compression load deformationtakes place so that the contact takes place over a certain area, whileat the same time the material is deformation annealed in this area,which is favourable from a resistance point of view. In order to satisfycasting demands the cylindrical contact surface of the hub shoulder canbe given a certain inclination.

According to one embodiment of the present invention the vane shoulderfurther has one at least partly cylindrical peripheral surface with ahole that extends through the shoulder, and the hub seat has a recesssituated radially inwards of the hub shoulder for frictional cooperationwith the cylindrical peripheral surface of the vane shoulder as well asa hole surrounded by an abutment surface arranged on the outside of thehub, whereby a clamping means is intended to be introduced through saidhole in order to, though pre-stressing, generate a frictional forcebetween vane shoulder and hub shoulder, which maintains an adjustedangular vane position.

By designing the seat of the hub with a recess having mutually inclinedsurfaces the torque can be taken up separately by a counteractingfrictional moment between the restriction surfaces of the recess and thevane shoulder. Advantageously, the clamping means can be comprised of athrough screw and nut and washer. When the screw is fastened with itsprestressing load two reaction forces result which to the rate will besubstantially larger than the clamping force because of the inclinedcontact surfaces. Thus an enlargement of the available counterfrictional moment will be achieved, since this is proportional to theresulting reaction forces.

According to a further embodiment of the invention, the hole in the seatof the hub has the form of a slit and the abutment surface for theclamping means is cylindrical. Hereby an adjustment of the vane blade indifferent angular positions is possible by that the clamping means firstis loosened, the vane blade is turned into the desired position and theclamping means is then fastened again.

According to an alternative embodiment of the invention the hole in thevane shoulder is designed to allow adjustment of the vane into differentangular positions in that the hole is formed as a slit. According to afurther development, the hole through the vane shoulder can be formed asa slit at the respective peripheral opening, tapering inwards towardsthe centre of the stud in order to have an extension substantiallycorresponding to the cross sectional form of the clamping means. Withthis design the position of the clamping means on the outside of the hubwill always be on the same place irrespective of the angular position,which facilitates assembly with machine tools. Change of the angularposition for all vanes on the hub can thus be made with only one tool.

According to a development of the invention the height of thecylindrical peripheral surface on the hub shoulder is adapted so thatthe frictional moment between the contact surfaces of the hub shoulderand the vane shoulder, respectively, has the ability to receive abending moment that is generated by air forces acting on the vane blade.The length of the cylindrical vane shoulder forms a lever for thisfrictional force and can be adjusted in order to take up the expectedbending moment.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings a preferred embodiment is shown, which isdescribed more specifically below, wherein

FIG. 1 shows a perspective view of a hub for a vane wheel,

FIG. 2 shows a partial perspective view of the hub of FIG. 1, seen fromthe opposite side,

FIG. 3a and 3b show a partial cross sectional view of the hub fromdifferent angles,

FIG. 4 shows a frontal view of the mounting part of a vane bladedesigned in accordance with the invention,

FIG. 5 shows an exploded view of part of the hub, the mounting part of avane blade as well as a clamping means,

FIG. 6 shows a view corresponding to that in FIG. 5 for an alternativeembodiment of the angularly adjustable mounting of the vane blade,

FIG. 6a shows a cross sectional view through the vane shoulder accordingto an advantageous embodiment, and

FIG. 7 shows a schematical, cross-sectional view, partly cut away, whichillustrates pre-stressing force vs. reaction forces at the mountingaccording to the invention.

DESCRIPTION OF A PREFERRED EMBODIMENT

In FIG. 1 a hub is shown, generally designed with 1, for a blade wheelwith a centre hole 2 and vane seats 3 evenly distributed over theperiphery. The seats are identical and only one seat will therefore bedescribed.

In FIG. 2 part of the opposite side of the hub shown in FIG. 1 is shown.In the embodiment shown each seat 3 has a slit 4, which slits on theside shown in FIG. 2 each are surrounded by a cylindrical abutmentsurface 5, the object of which will be described more in detail below.Further, the seats are evenly distributed over the periphery of the hub.Vanes 6 are clamped in the seats 3 with the aid of clamping means, whichin the embodiment shown are comprised of bolt 7 with nut 8.

In FIG. 3a a partial cross sectional perspective view of a seat 3 isshown and in FIG. 3b the same partial cross sectional view is shown fromthe side. The seat 3 comprises a shoulder 10 extending beyond a recess 9in the hub 1, which shoulder surrounds an opening 11 confined on threesides and open on the fourth side for the insertion of a vane stud. Theextending shoulder has a partly cylindrical contact surface 12.

The slit 4 is arranged in the bottom of the recess, i.e. the radial partof the hub, towards which the two opposite sides 13,13' (only one isshown in this view) converge.

In FIG. 4, a vane 6 is shown with vane blade 15, vane stud 16 and a vaneshoulder 17 provided on the stud. When putting together the parts, thestud 16 is introduced into the opening 11 so that the vane shoulderlands in the recess 9 of the seat. The vane shoulder 17 has acylindrical peripheral surface 18 as well as a partly spherical contactsurface 19 facing the vane and surrounding the stud. Further, a throughhole 20 is arranged in the shoulder 17.

Further, in FIG. 4 is schematically shown the abutment surface 21,21'resulting from the compressive load deformation between the partlyspherical contact surface 19 on the vane shoulder 17 on the one side andthe partly cylindrical contact surface 12 on the hub shoulder 10, on theother side. The centrifugal force acting in the direction of the arrow Cresults in yield and said deformation. The size of the area 21,21' ismuch over-emphasized in the figure. With the structure according to theinvention is achieved that, irrespective of the angular position of thevane, the geometrical position of the contact will always be exactly thesame. Because of the yield the material is strain-hardened.

In FIG. 5 an exploded view is shown with the vane 6 above the seat 3. Atassembly the vane shoulder 17 is put into the recess 9. The bolt 7 isintroduced through the hole 20 in the vane shoulder and through the slit4, whereupon the nut 8 is fastened from the opposite side of the hub.

In FIG. 6 a view corresponding to that in FIG. 5 is shown. Hereby theangular adjustability is arranged in the vane shoulder contrary to theprevious embodiment. Thus the slit 4 in the recess 9 of the seat 3 isreplaced by a hole 22 while the hole 20 in the vane shoulder 17 isreplaced by a slit 23. Thanks to the conically tapering recess 9 of theseat the slit may be through without affecting the axial alignment ofthe vane. In order to secure the axial alignment of the vane, however,the slit 23 in the vane shoulder may be designed as is shown in FIG. 6a,at 23', so that its middle part has a cross section which substantiallycorresponds to the cross section of the clamping means, while it isenlarged towards the respective peripheral opening.

In FIG. 7 a partly cutaway cross sectional view is schematically shown,taken through a recess in the hub and the vane shoulder providedtherein. Thanks to the design of the recess with two surfaces 13,13'converging towards each other, the force F, which is applied with theaid of a clamping means through the vane shoulder and the hub, givesrise to two reaction forces, which are totally equal to R, and in thecase shown, where the force F acts in the direction towards the point ofintersection of the two converging surfaces 13,13', the reaction forcesare each equal to R/2. At other angular adjustments the reaction forceswill be unequal, but the size of the sum of the two reaction forces isstill substantially as large. The size of the reaction forces inrelation to the pre-stressing force depends on the angle choosen for thetwo surfaces converging towards each other and can be made larger orsmaller. In the case shown with a convering angle of about 19°, R willbe about 3×F.

The cylindrical part of the vane shoulder will act as a lever for thefriction between the contact surfaces 12 and 19 and by adapting thisheight to the expected bending moment which is generated by the airforces acting on the vane blade, this can be compensated for with thedesired safety.

Experimental Results Test 1

The mounting according to the invention was tested in view of inherentfrequency as well as endurance limit for vane stud and hub seat.

With an absolutely fixed mounting the theoretical inherent frequency is108 Hz. The lowest inherent frequency for the mounting according to theinvention was 100 Hz, which is a very good result.

Test 2

In order to make sure that the angular position of the vanes are notchanged because of the torque load a frictional moment of 38 Nm isnecessary. In the tests a tightening moment for the screw passingthrough the vane stud and the slit in the hub seat being 25 Nm was used.Hereby a frictional moment of 125 Nm was obtained, which gives tripplesafety.

Test 3

The endurance limit should be such that the probability for rupture doesnot exceed 1/1000 for 50,000 start and stop cycles. In the test, forthis probability at least 113,000 cycles for the vane stud was achieved,while for the hub no ruptures were obtained in any test after more than200,000 cycles.

The above tests show that the mounting according to the invention isextremely dependable and makes possible a structure with more thantripple safety without that the components used have to be dimensionedmore strongly compared with known structures.

Within the scope of the invention variations of the above describedembodiment which at the time of the present application is the preferredembodiment of the invention, can be made. Thus, the clamping means maybe comprised of a screw with nut and washer, but could also be comprisedof a pull rod with a suitable lock outside the hub, in order to make anadjustment of the vane angles more convenient. Further, the design ofthe peripheral surface of the vane shoulder can be choosen otherwise incombination with another form of the recess in the seat of the hub.

We claim:
 1. A vane suspension for angle adjustable mounting of a vane,comprising a vane and a hub having a center, a seat in the hub whichreceives a portion of the vane, said vane including a vane blade, a studand a vane shoulder provided at an end of the stud, said vane shoulderhaving a partly spherical contact surface facing the vane blade, theseat of the hub having a hub shoulder with a partly cylindrical contactsurface radially facing toward the center of the hub, the partlyspherical contact surface of the vane shoulder and the partlycylindrical contact surface of the hub shoulder being arranged tomutually cooperate along a pair of linear contact regions, whereby theposition of the linear contact regions is constant irrespective of anangular position of the vane in relation to the hub.
 2. A vanesuspension according to claim 1, wherein the vane shoulder has an atleast partly cylindrical peripheral surface with a bore passing throughthe vane shoulder, the seat of the hub having a recess situated radiallyinwards of the hub shoulder for frictional engagement with the at leastpartly cylindrical peripheral surface of the vane shoulder and a boresurrounded by an abutment surface provided outside the hub, andfastening means having a portion positionable in said bore of the seatto create a frictional force between the vane shoulder and the seat ofthe hub to maintain an adjusted vane angle position, usingpre-stressing.
 3. A vane suspension according to claim 2, wherein thebore in the seat of the hub is a slit, the abutment surface againstwhich abuts a portion of the fastening means having a cylindrical shape.4. A vane suspension according to claim 2, wherein the bore in the vaneshoulder is a slit, the bore in the seat corresponding in shape to across section of one portion of the fastening means so that anotherportion of the fastening means lying outside the hub has a fixedposition in relation to the hub regardless of the angular position ofthe vane blade.
 5. A vane suspension according to claim 2, wherein thebore through the vane shoulder has a middle part possessing a crosssection that substantially corresponds to a cross section of a portionof the fastening means, said bore in the vane shoulder being enlargedaway from the middle part.
 6. A vane suspension according to claim 2,wherein the fastening means includes a through bolt and a nut arrangedoutside the hub.
 7. A vane suspension according to claim 2, wherein thecylindrical peripheral surface of the vane shoulder has a heightsufficient to receive a bending moment generated by air forces acting onthe vane blade.
 8. A vane suspension according to claim 1, wherein theseat of the hub comprises two inclined surfaces arranged at an acuteangle relative to each other.
 9. A vane suspension according to claim 3,wherein the fastening means includes a through bolt and a nut arrangedoutside the hub.
 10. A vane suspension according to claim 4, wherein thefastening means includes a through bolt and a nut outside the hub.
 11. Avane suspension according to claim 3, wherein the cylindrical peripheralsurface of the vane shoulder has a height sufficient to receive abending moment generated by air forces acting on the vane blade.
 12. Avane suspension according to claim 4, wherein the cylindrical peripheralsurface of the vane shoulder has a height sufficient to receive abending moment generated by air forces acting on the vane blade.
 13. Avane suspension according to claim 5, wherein the cylindrical peripheralsurface of the vane shoulder has a height sufficient to receive abending moment generated by air forces acting on the vane blade.
 14. Avane suspension according to claim 6, wherein the cylindrical peripheralsurface of the vane shoulder has a height sufficient to receive abending moment generated by air forces acting on the vane blade.
 15. Avane suspension according to claim 9, wherein the cylindrical peripheralsurface of the vane shoulder has a height sufficient to receive abending moment generated by air forces acting on the vane blade.
 16. Avane suspension according to claim 2, wherein the recess in the seat ofthe hub comprises two inclined surfaces arranged at an acute anglerelative to each other.
 17. A vane suspension according to claim 3,wherein the recess in the seat of the hub comprises two inclinedsurfaces arranged at an acute angle relative to each other.
 18. A vanesuspension providing an angle adjustable mounting of a vane, comprisinga vane and a hub, said vane including a vane blade and a mounting part,the mounting part having a vane shoulder provided with a partlyspherical contact surface that faces towards the vane blade, said hubincluding a seat provided with a recess for receiving at least a portionof the mounting part, said seat having a hub shoulder provided with apartly cylindrical contact surface which engages the partly sphericalcontact surface of the vane shoulder.
 19. A vane suspension according toclaim 18, including a through bore extending through the hub and openinginto the seat, and including fastening means for securing said vanerelative to said hub, a portion of said fastening means extendingthrough the bore in the hub.
 20. A vane suspension according to claim19, wherein said mounting part includes a through hole for being alignedwith the through bore in the hub and for receiving a portion of thefastening means.